Multi-Band Analogue Electromagnetically Induced Transparency in DoubleTuned Metamaterials

A multi-band analogue electromagnetically induced transparency (A-EIT) metamaterial is proposed. The structure is composed of liquid crystal (LC) layer and a graphene strips layer on both sides of silicon dioxide. The transmission spectrum and electric field distribution of only one graphene strip and two graphene strips have been studied. As a bright mode, the graphene strip is coupled with adjacent graphene strip to realize the A-EIT effect. When multiple graphene strips are coupled with each other, the multi-band A-EIT is obtained due to the electric dipole resonances of the four strips. The results show that the multiband A-EIT effect can be tuned by voltage on LC and graphene layer, respectively. Moreover, changing the incident angle of the electromagnetic wave has had little influence on the transmission window in the low frequency band, it is meaning that the A-EIT effect with insensitive to the incident angle can be obtained. Each transmission window has a high maximum transmittance and figure of merit (FOM). The multi-band A-EIT effect can widen the application on sensor and optical storage devices.

Terahertz Transmission Characteristics of Double-Layer Plasmonic Metamaterial and LC-Based Structure

In this paper, we present a novel design of an electrically tunable metamaterial device in the terahertz frequency range of 325–500 GHz. The device is analyzed and optimized using an equivalent circuit and numerical simulation. The experimental and simulation results are almost identical in the entire design frequency range. A maximum modulation depth of 90.87% is achieved in the transmission window. The bandpass width decreases from 102.55 to 28.7 GHz as the bias voltage increases from 0 to 30 V. This structure provides new insights into the potential of electrically tunable terahertz devices for a wide range of applications.

Determination of active ingredients in commercial insecticides using spectral characteristics of Fourier transform infrared spectroscopy (FTIR)

Pesticides have become a basic necessity for yield development. This might be credited to the quickly expanding population, which has presented weight on the food creation industry.Fourier Transform Infra-red Spectroscopy utilizes sample with less course of action, less time consuming, simple, fast, non-destructive and environmental friendly infrared-based method. It makes use of Smart iTR window and pellets use on omnic transmission window. In FTIR the peaks formed for the representative sample are from 800 cm-1 to 4000 cm-1 of wavenumbers against the % transmittance. The FTIR spectra obtained for pesticide formulations were on par with the NIST (National Institute of Standards and Technology) spectra library. Comparing the commercial-grade spectra with the Spectrabase, NIST library and Bio-rad software showed the peak ranges for different functional groups of the compound and can be examined with KnowItAll software’s ProcessItIR and AnalyseItIR. We can obtain the active principle of the peak, peak intensities. This method can be viewed as genuine choices to long and tedious chromatographic strategies as a rule suggested for quality control of commercially accessible pesticide formulations and check for adultered formulations that harm agricultural produce.

Tunable Transmissive Terahertz Linear Polarizer for Arbitrary Linear Incidence Based on Low-Dimensional Metamaterials

In this work, we propose a structure consisting of three metamaterial layers and a metallic grating layer to rotate the polarization of arbitrary linearly polarized incidence to the y-direction with high transmissivity by electrically tuning these metamaterials. The transfer matrix method together with a harmonic oscillator model is adopted to theoretically study the proposed structure. Numerical simulation based on the finite difference time-domain method is performed assuming that the metamaterial layers are constituted by graphene ribbon arrays. The calculation and simulation results show that the Drude absorption is responsible for the polarization rotation. Fermi level and scattering rate of graphene are important for the transmissivity. For a polarization rotation of around 90°, the thickness of either the upper or lower dielectric separations influences the transmission window. For a polarization rotation of around 45° and 135°, the lower dielectric separations decide the frequency of the transmission window, while the upper dielectric separations just slightly influence the transmissivity.

Genesis and influencing factors of the colour of chrysoprase

The genesis and influencing factors of the colour of chrysoprase were studied based on the results of transmission electron microscopy and X-ray fluorescence, ultraviolet–visible and Raman spectroscopies. The results show that under a 6504-K fluorescent lamp, chrysoprase colour is divided into the grades of fancy, fancy intense and fancy deep. The lightness of chrysoprase is affected mainly by its chromium content, the chroma is affected by its nickel content and the hue angle is affected by the sum of its chromium and ferrum contents. The colour of chrysoprase is related significantly to the transmission window that occurs between the two main bands centred at 380 and 660 nm and the absorption peaks at 380 and 660 nm in the ultraviolet–visible spectrum. Chrysoprase with low crystallinity has more nickel and a higher chroma. The inclusions that cause the chrysoprase colour have been identified as pimelite.

Nano-Crystallization of Ln-Fluoride Crystals in Glass-Ceramics via Inducing of Yb3+ for Efficient Near-Infrared Upconversion Luminescence of Tm3+

Transparent glass-ceramic composites embedded with Ln-fluoride nanocrystals are prepared in this work to enhance the upconversion luminescence of Tm3+. The crystalline phases, microstructures, and photoluminescence properties of samples are carefully investigated. KYb3F10 nanocrystals are proved to controllably precipitate in the glass-ceramics via the inducing of Yb3+ when the doping concentration varies from 0.5 to 1.5 mol%. Pure near-infrared upconversion emissions are observed and the emission intensities are enhanced in the glass-ceramics as compared to in the precursor glass due to the incorporation of Tm3+ into the KYb3F10 crystal structures via substitutions for Yb3+. Furthermore, KYb2F7 crystals are also nano-crystallized in the glass-ceramics when the Yb3+ concentration exceeds 2.0 mol%. The upconversion emission intensity of Tm3+ is further enhanced by seven times as Tm3+ enters the lattice sites of pure KYb2F7 nanocrystals. The designed glass ceramics provide efficient gain materials for optical applications in the biological transmission window. Moreover, the controllable nano-crystallization strategy induced by Yb3+ opens a new way for engineering a wide range of functional nanomaterials with effective incorporation of Ln3+ ions into fluoride crystal structures.

Genesis and Influencing Factors of the Colour of Chrysoprase: Colourimetric Analysis Based on the Cie 1976 L*a*b* Uniform Colour Space

The colour of chrysoprase is produced by Ni cations and influenced by other transition-metal cations and crystallinity. Presented here is a study of the origin of chrysoprase colour and an exploration of the factors that influence it from the perspective of gemstone chromaticity. Transmission electron microscopy and X-ray fluorescence, ultraviolet–visible and Raman spectroscopies are used to investigate 41 gem-quality chrysoprase samples, and the results show that chrysoprase colour results from nanometre-size inclusions of pimelite. Under a 6504-K fluorescent lamp, chrysoprase colour is divided into the grades of fancy, fancy intense and fancy deep. The lightness of chrysoprase is affected mainly by its Cr content, the chroma is affected by its Ni content and the hue angle is affected by the sum of its Cr and Fe contents. Chrysoprase hue and chroma are related significantly to the transmission window that occurs between the two main bands centred at 380 and 660 nm and the absorption peak at 660 nm in the ultraviolet–visible spectrum. Chrysoprase with low crystallinity has more Ni and a higher chroma.